1. Field of the Invention
This invention relates to a method and equipment for producing a gas separator of fuel cells, which is integrated with a gas flow channel.
2. Description of the Related Art
Fuel cells generating electric power in response to the feed of fuel gas are generally manufactured by integrating plural electric cells. A separator lies between adjacent cells for the separation of both of them and additionally takes a role of material for forming a gas flow channel through which fuel gas is fed to the respective cells. With regard to techniques for forming a recessed portion (groove or depression) changing into a gas flow channel in a separator integrated with a gas flow channel like this, cutting method for machine cutting a metal plate changing into a base material of a separator to form grooves and the like, press working method for subjecting a metal plate changing into a base material of a separator to press working to form grooves and the like by stamping, and etching method for subjecting a metal plate changing into base material of a separator to etching to form chemically grooves and the like are known.
According to the cutting method, processing accuracy of grooves and depressions can be improved. In contrast with this, this method has such drawbacks that if the shape of a gas flow channel becomes complicated, gross floor area becomes increased, and at the same time, great time is necessary for processing and yet, production cost becomes high. The press working method is convenient for mass production because of high processing accuracy and very small fluctuation between lots. However, this method has such drawbacks that production cost of a press die is high, work hardening as well as local change of wall thinning cannot be avoided, and sufficient guarantee cannot be given in respect the durability, i.e., changing with the lapse of time such as corrosion resistance and the like. Further, according to the above described conventional etching method, an etching solution such as electrolytic solution and the like is prepared in a fixed vessel, and a metal plate to be changed into a base material of a separator is immersed in the etching solution to carry out etching. However, such a dipping-like method shows a tendency that a long processing time is required because the etching solution as well as reaction products migrates slowly around the face to be processed. Particularly, in case of electrolytic etching by the use of electrodes, even when a feed current is increased, a fresh etching solution proportional to the current is hard to be fed to the face to be processed within a short time. Accordingly, such drawbacks are caused that a long period of time is required for making grooves, in particular in case where the groove is required to have a depth of several hundred micrometers, productivity is low, and production cost becomes high.
It is an object of the present invention to provide a method for producing a separator, of fuel cells, which is capable of producing a separator integrated with a gas flow channel efficiently at comparatively low costs and which causes no trouble in respect of processing accuracy and durability. It is also an object of the present invention to provide an equipment for producing a separator of fuel cells with the object of putting the production method into practice effectively.
According to a first aspect of the present invention, there is provided a method for producing a separator for use in fuel cells, which is integrated with a gas flow channel, and characterized by comprising: a masking step of partially masking the face to be processed of a base material of a separator; an electrolytic processing step of disposing an electrode oppositely to the masked face of the base material to be processed, injecting and feeding an electrolytic solution to the face to be processed from a direction which makes almost a right angle with the face to let the electrolytic solution lie between the face and the electrode, and electrolyzing the unmasked portion of the face under the condition of feeding electricity to the electrode and at the same time to the base material to form recessed portions for making the gas flow channel; and a mask-removing step of removing a mask from the face after forming the recessed portions.
According to this constitution, an electrolytic solution is injected and fed to the partially masked face to be processed of a base material of a separator from a direction which is almost at right angles to the face so that the electrolytic solution instantly spreads all over the area between the face and the electrode. Accordingly, the whole face to be processed can be covered with the electrolytic solution all around. In particular, as the feed direction of an electrolytic solution is almost perpendicular to the face to be processed, the electrolytic solution can be fed directly to the central area of the face too. In this point, the feed efficiency of the electrolytic solution is very good as compared with the case where the electrolytic solution is poured in parallel to the face to be processed from the end of the base material. As a result, by virtue of the feed action of the electrolytic solution induced by injection, a sufficient amount of fresh electrolytic solution is fed one after another between the face to be processed and the electrode, and at the same time, unnecessary electrolysis products are washed away over the face to the outside. Accordingly, the electrochemical reaction at the unmasked portion of the face is promoted. Consequently, desired recessed portions for making a gas flow channel can be formed on the unmasked portion of the face with high energy efficiency within comparatively short time.
According to a second aspect, in the method of the first aspect, the method is characterized in that the electrode is a plane-facing electrode to be disposed oppositely to the face to be processed at a predetermined interval, and has a nozzle to inject and feed an electrolytic solution to the face to be processed from a direction which is almost perpendicular to the face. In this method, in connection with the feature that an electrolytic solution is injected and fed to the face to be processed from a direction that is almost perpendicular to the same face, it is preferable to provide an electrolytic solution injection feed structure in the electrode facing the face to be processed. Taking this point into consideration, the second aspect is contrived.
According to a third aspect, in the method recited in the first or second aspect, the method is further characterized in that the base material of a separator has a shape of a flat plate, both faces of the base material being to be processed, and an electrolytic solution is fed toward the both faces by injection from a direction which is almost perpendicular to each of the both faces. Ac cording to this method, recessed portions for making a gas flow channel can be formed simultaneously on both sides of the flat base material of a separator, and accordingly, working efficiency improves. In addition to this, the flat base material can be held stably in position during the electrolytic processing so that electrolytic processing accuracy can be improved. Namely, in case of injecting an electrolytic solution at the same time to both the faces to be processed in/from a direction which is almost perpendicular to the respective face, both of the liquid injections are opposite to each other, and when both injection pressures are almost the same with each other, the liquid injections have a relation that they mutually support the backside of the base material and cancel mutual effects thereby. Accordingly, the flat base material can be held stably in position, and the respective face to be processed can undergo uniform electrolysis.
According to a fourth aspect, in the method of the first to third aspects, the method is characterized in that the base material is maintained almost in a vertical direction, and an electrolytic solution is fed by injection to the perpendicularly extending face to be processed from a direction that is almost horizontal. According to this constitution, an electrolytic solution sprayed to the face to be processed can flow down by itself along the face extending perpendicularly under the influence of gravity. Accordingly, an old electrolytic solution is smoothly replaced with a new one on the face to be processed, and the efficiency of electrolytic processing improves thereby.
According to a fifth aspect, in the method of the first to fourth aspects, the method is farther characterized in that an electrolytic solution once fed by injection to the face to be processed is recovered, pumped up and fed again to the face to be processed. This constitution makes it possible to use the electrolytic solution dropped out of the face to be processed again. Further, introduction of the combination of the 3rd, 4th and 5th aspects makes it possible to perform continuous production of separators of fuel cells. This will promote industrial realization of fuel cells.
According to a 6th aspect, there is provided an equipment for producing a separator of fuel cells, which is integrated with a gas flow channel, and characterized by comprising: a holder for holding a base material of a separator having a face to be processed which is partially masked; a plane-facing nozzle, used also as an electrode, disposed oppositely to the face held by the holder and having a guide passage which makes it possible to feed an electrolytic solution to the face by injection from a direction that is almost perpendicular to the face; an electricity feeding unit for supplying an electric current to the base material and also to the nozzle; a recovery unit for recovering an electrolytic solution flowed out after injecting the electrolytic solution from the nozzle to the base material; and a feed unit for feeding again the electrolytic solution recovered in the recovery unit.
By using this production equipment, the aforementioned production method can be effectively put into practice. Namely, when an electrolytic solution is injected and fed to the face to be processed of the base material held by the holder out of the plane-facing nozzle disposed oppositely to the face, unmasked portion of the face in the electrolytic solution is electrolyzed by virtue of an electric current fed by the electric feeding unit to form recessed portions for making a gas flow channel. An electrolytic solution injected to the base material of a separator and then flowed out is recovered by the recovery unit and fed again to the nozzle by the feed unit. Accordingly, this equipment makes it easy to perform continuous production of separators for use in fuel cells.
According to a 7th aspect, the equipment is characterized in that a pair of the nozzles are provided and disposed in such a way that respective injection hole of the nozzles on one side is opposite to that on another side, and the holder allows to dispose the base material between a pair of the nozzles. Technical significance of the 7th aspect is almost the same with that of the 3rd aspect aforementioned.
According to an 8th aspect, the equipment is further characterized in that the holder holds the base material in such a way that the direction of the face to be processed is disposed almost vertically. Technical significance of the eighth aspect is almost the same with that of the fourth aspect aforementioned. It is preferred to functionally connect/couple the holder recited in the 6th, 7th, and 8th aspects for holding a separator with a predetermined carrier. This makes easy to construct a mass production system of separators of fuel cells.